1. Field of the Invention
The present invention relates to asymmetric styrene derivatives having carbazole and aniline and organic light emitting diode using the same, and particularly to asymmetric styrene derivatives having carbazole and aniline provided with main BCzVBi structure but impair the symmetry of BCzVBi, and organic light emitting diode using the same.
2. Description of the Prior Art
OLED (organic light emitting diode), also commonly known as an organic electroluminescent device, is kind a light emitting diode (LED) having organic layer as active layer. Since the organic electroluminescent device provides advantages of self-illumination, wider visual angle (>170°), shorter response time (˜μs), higher contrast, higher efficiency, lower power consumption, higher brightness, low operate voltage (3-10 V), thinner size (<2 mm), flexibility and the like, it has been gradually used in flat panel display in recent years. In comparison to liquid crystal display, the organic electroluminescent device provides with OLED pixel array having self-luminous characteristics and therefore do not require additional back light module; to apply OLED into a full-color display, it is necessary and important to develop red, green, and blue light emitting materials with appropriate chromaticity and high light-emitting efficiency.
Excitons generated from recombining holes and electrons may have triplet state or singlet state for its spin state. Light emitted from singlet exciton radiates fluorescence and light emitted from triplet exciton radiates phosphorescence. Phosphorescence achieves 3-fold efficiency comparing to fluorescence and may greatly enhance the IQE (internal quantum efficiency) of devices up to 100% by adopting metal complexes in electroluminescent configuration to achieve strong spin-orbital coupling and mixing of singlets and triplets. Therefore, phosphorescent metal complexes are now adopted as phosphorescent dopants in the emitting layer of OLED. In addition, the doping method of doping the emitting material into host emitting material is generally used to reduce the self-quenching of the emitting material. Therefore, the search for host emitting materials becomes noteworthy since host emitting materials must be capable of capturing carriers and have good energy transfer properties, high glass transition temperature, high thermal stability and appropriate energy gap of the singlet and triplet excited states. However, it would be difficult to obtain host emitting materials that fully meet the criteria and there is still some room for host emitting material development in OLED.
The hunt for efficient blue electroluminescence material is of particular interest because it is an essential component to realize OLEDs in display as well as lighting applications. Many research groups have successfully prepared efficient blue fluorophores and the OLED thereof. However, the efficient ones with good Commission Internationale d'Énclairage y coordinate value (CIEy) ≦0.15 are still relatively rare. At the present time, there is a lack of good organic electroluminescence compounds that will satisfy the aforementioned need.